MRI Pelvis — cervical cancer staging

Whole pelvis including the parametria, pelvic sidewalls and ureters, extended superiorly to the renal hila for para-aortic nodes and hydronephrosis.

Typical, not policy

Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.

Premedication

Given to make the acquisition work, not to treat the patient. Doses are typical — confirm against your local protocol and prescribe within your own governance.

Hyoscine butylbromide (Buscopan), or glucagon where unavailable — where locally used

Suppression of small bowel and rectal peristalsis over the pelvis. Parametrial invasion is called on interruption of a low-signal stromal ring that is a couple of millimetres thick on a small-field-of-view oblique T2; ghosting from adjacent bowel across that ring is the mechanism by which a technically limited study becomes an overcalled stage, and overcalling parametrial invasion moves a patient from surgery to chemoradiotherapy.

Dose and route: Typically 20 mg intravenously, or about 20 mg intramuscularly where the study is unenhanced and no cannula is otherwise required. Glucagon roughly 0.25-1 mg intravenously as the substitute.
When: Immediately before the small-field-of-view oblique T2 and diffusion series, which are the decisive acquisitions. The effect is shorter than the examination, so a single dose should be timed to those sequences rather than to the start.
Do not give if: If glucagon is used instead of hyoscine, it carries its OWN absolute contraindications rather than inheriting a clean slate: phaeochromocytoma, where it provokes catecholamine release and hypertensive crisis, and insulinoma or glucagonoma, where it causes rebound hypoglycaemia. It also raises blood glucose transiently, which matters in diabetes, and commonly causes nausea and vomiting.
MHRA Drug Safety Update (February 2017), issued after nine reported deaths mostly from cardiac arrest: in patients with cardiac disease, monitor the patient and ensure resuscitation equipment AND staff trained to use it are readily available before giving it. This is an availability requirement, not a caution to note and move past.
Practice varies, and this protocol already carries a second variable practice in the use of vaginal gel — neither is universal, and the local protocol governs both.
Contraindicated in untreated angle-closure glaucoma, myasthenia gravis, megacolon, and significant tachyarrhythmia.
Caution in prostatic enlargement with urinary retention, and in significant cardiac disease.
Warn the patient about transient blurred vision, and that they must not drive until it resolves.
If unsuitable: Proceed without it and repeat the oblique-axial T2 if it is degraded. Where motion persists, saturation bands over anterior subcutaneous fat and swapping the phase-encoding direction move the ghosting away from the cervix, which is often more effective than a second dose.

When to use it

Newly diagnosed cervical carcinoma requiring tumour size, parametrial and vaginal extension assessment.
Selection between surgery and chemoradiotherapy.
Assessment before fertility-sparing trachelectomy, where the distance from tumour to internal os is decisive.
Detection of hydronephrosis and nodal disease.
Assessment of recurrence or response after chemoradiotherapy.

Technique

Sagittal T2, plus oblique-axial T2 perpendicular to the cervical canal and oblique-coronal T2 parallel to it — the parametrial assessment depends entirely on these planes.
Thin slices and a small field of view over the cervix, with a separate large field-of-view axial for nodes and the upper abdomen.
Diffusion-weighted imaging in the oblique-axial plane for tumour extent and nodal assessment.
Vaginal gel is used in some centres to distend the fornices; it is not universal.

Where it goes wrong

Planes referenced to the patient rather than to the cervical canal, which is the standard cause of parametrial overcall.
Field of view too large to resolve the low-signal cervical stromal ring, the structure whose interruption defines parametrial invasion.
Superior coverage stopping at the pelvic brim and missing para-aortic nodes and hydronephrosis.
Post-cone-biopsy oedema mimicking residual tumour when the study is done too soon after the procedure.

Clinical questions that reach this study

Suspected ectopic pregnancy Acute pelvic pain in the reproductive age group (including suspected PID and tubo-ovarian abscess)Suspected ovarian (adnexal) torsion Adnexal mass — characterisation and risk stratification Suspected endometriosis, including deep disease Abnormal uterine bleeding and endometrial assessment Suspected ovarian cancer or indeterminate adnexal mass Endometrial cancer — staging Cervical cancer — staging

Contrast

NoneGadolinium, intravenous

Where used, a macrocyclic gadolinium agent at a typical single dose of about 0.1 mmol/kg.

High-resolution T2 with diffusion answers most of the local staging question; contrast is added mainly for suspected fistula, bladder or rectal invasion, and for small-volume or post-treatment disease. Practice differs on whether it is routine.

Acquisition

Breathing: Free breathing with an antiperistaltic agent.
Preparation: Moderate bladder filling is wanted for most gynaecological protocols; an over-full bladder causes motion and an empty one loses anatomical separation. Fasting for a few hours plus an antiperistaltic agent reduces bowel motion for high-resolution sequences. Intrauterine devices are MR-conditional in general but must still be declared at screening.

Safety checks this protocol carries

Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.

Kidney function and gadolinium-based contrast· radiographer at scan
MR safety screening for implants and foreign bodies· radiographer at scan
Gadolinium in known or possible pregnancy· radiographer at scan